Sticking to one type, the fishes are difficult to get competitive with although pretty fun. With our sharks getting newer support, I see further hybrids with this card pulling of some miracles. Video of wins at the bottom of the page.
Super Ancient Deepsea Kin Coelacanth
Left-Hand Shark X3
Right-Hand Shark X3
Eater Of Millions
Tin Goldfish X3
Fishborg Archer X3
Lifeless Leaffish X3
Moon Mirror Sheild X2
Power of the Guardian
Moray of Greed X2
Rank-Up Magic – The Seventh One X2
Fish and Swaps
Fish Depth Charge X3
Oh Fish! X3
White Aura Monoceros
Clear Wing Synchro Dragon
Trishula, Zero Dragon of the Ice Barrier
Trusgula, Dragon of the Ice Barrier
Evilswarm Excition Knight
Number 39: Utopia
Number 101: Silent Honor ARK
Number S39: Utopia Prime
Number C101: Silent Honor DARK
Number S39 Utopia The Ligtening
Number 104: Masquerade
Number 41: Bagooska the Terribly Tapir
Number C104: Umbral Horror Masquerade
Number 47: Nightmare Shark
The main cards are Right and Left-Hand sharks and their extra abilities to protect level 4 XYZ monsters well. If they are held by those extra monsters, one makes it cannot be destroyed by battle and the other cannot be destroyed by a card effect. Have the Left one already in the graveyard and you can pull off this combo in one shot unless countered. Then a downside in using the level 4 XYZ is you will have to get rid of one of these protects to activate its normal effect.
Speaking of countered, Oh Fish! is your biggest counter with multiple other cards in this deck to the banish zone. To then return to the deck once activating this to negate a monster effect. White Aura gets the job done with this as you can banish a Water-type in the graveyard to consistently summon it back to the field. Then Fishborg and the Left/Right Hand Shark can banish themself.
Some other stalling cards include Peace of the Messenger, Fish Depth Charge, Clear Wing Synchro Dragon and Eater of Millions
Other draw cards aside from Right-Hand and Lifeless Leafless include Whitefish Salvage, White Mirror and Fish and Swaps.
Flying Carp to summon Deepsea King with summons 4 fish monsters from the deck to then get two extra deck monsters on the field. This strat works well with a Moon Mirror Sheild or Power of the Guardian as it needs to destroy a monster first. Or save these equip cards as it rises in the attack by discarding any card in the hand.
Rank-Up-Magic here only works if you draw it from the deck. Then if you have not already used Number 101 or 104, you can summon their upgrades immediately.